1. Field of the Invention
The present invention relates to a method of producing crude oil. The present invention particularly relates to a method of producing crude oil using a gas lift process.
2. Background of the Art
Oil from oil bearing earth formations is usually first produced by the inherent formation pressure of the oil bearing earth formations. In some cases, however, the oil bearing formation lacks sufficient inherent pressure to force the oil from the formation upward to the surface. In other cases, the inherent pressure of an oil-bearing formation can be expended prior to the recovery of all of the recoverable oil so that when the pressure of the production zone has been reduced by continued withdrawal, the well will stop flowing. When this occurs, artificial methods of lifting the oil from the formation to the surface are usually employed.
One method of continuing production is to provide mechanical pumping operations wherein the pump is located at the surface. In U.S. Pat. No. 3,963,377 to Elliott, et al., a pneumatically powered submerged pump for lifting high viscosity oil from an oil well is disclosed. Another popular method for achieving production from wells that no longer are capable of natural flow is by the gas lift method.
Gas injection into an oil well is a well-known artificial lift method for facilitating oil recovery from the oil well. This method is commonly referred to as gas lift recovery or, most often, simply as a gas lift. A typical gas lift method provides a lift gas at the surface that is conveyed to a surface wellhead connection where the lift gas is injected into the casing-tubing annulus of the well. Upon injection, the lift gas travels down the casing-tubing annulus to a plurality of specially designed subsurface gas injection valves that enable the lift gas to enter the tubing string. The lift gas commingles with the formation fluids in the tubing string, lifting the formation fluids up the tubing string to the surface.
As is taught in U.S. Pat. No. 5,871,048 to Tokar, et al., there are significant operational costs associated with gas injection. In Tokar, a method for automatically determining an optimum gas rate is disclosed. While determining the optimum gas flow is an important element in gas lift methods, it is by no means the only factor that should be considered when optimizing a gas lift method for recovering oil from an oil well.
It would be desirable in the art of producing oil from oil wells to economically produce oil using a gas lift method. It would be particularly desirable to reduce the cost of producing crude oil using a gas lift method of recovery. Accordingly, it is desirable to economically optimize the gas injection lift method such that the operational costs for the well are balanced with the oil production revenue from the well.